A multi-core cable that is a cable set having a number of cores is used, for example, as a probe cable of an ultrasonic diagnostic apparatus that is a medical apparatus, a medical cable such as an endoscope cable, or a control cable of a robot for which precise control is required. As these medical apparatuses or control devices become small and light, a reduction in the diameter of the cable for transmission of signals, power, and the like in the apparatuses or devices has been requested. For this reason, development of technology to reduce the diameter without degrading the electrical performance and the like of the cable has been requested.
Meanwhile, with the diversification and increases in the capacity and speed of transmitted information signals, there is also high demand to increase the number of signal lines or the number of power lines while reducing the diameter of the transmission cable as much as possible.
As the transmission cable disclosed in JP-T-2002-515630, a transmission cable using coaxial cables with small outer diameters as multiple cores is used.
The conventional transmission cable described above has excellent electrical characteristics as a coaxial cable. However, as the number of signal lines or the number of power lines is increased, the outer diameter of the cable is also increased. A further study to make the diameter reduction and the increase in the number of wires compatible with each other has not been made. Accordingly, for example, in a medical cable inserted into the blood vessel, it has been difficult to meet the demands of having an ultrafine diameter and information transmission of higher quality.